Process for accelerating metallurgical reactions

ABSTRACT

A process for accelerating a metallurgical reaction in which metal and slag are produced which comprises moving a stream of metal continuously in a countercurrent direction to slag moved within a channel and injecting at least one jet of an inert gas on the melt into a marginal region of the channel parallel to and/or at an inclination to the boundary formed by the metal and slag; and an apparatus therefor.

United States Patent [1 1 Steinmetz et al.

[ 1 Jan. 21, 1975 PROCESS FOR ACCELERATING METALLURGICAL REACTIONS Inventors: Eberhard Steinmetz; Jurgen Kuhn,

both of Bochum, Germany Gesellschaft zur Forderung der Eisenhuttentechnix Gmbl-l, Dusseldorf, Germany Filed: Feb. 14, 1972 Appl. No.: 226,303

Assignee:

Foreign Application Priority Data Feb. 16, 1971 Germany 2107263 US. Cl 75/93 R, 75/60, 75/63 Int. Cl C221) 9/12 Field of Search 75/93, 63, 40, 60, 49;

References Cited UNITED STATES PATENTS 7/1909 Larsen 75/11 2,918,365 12/1959 Kanamori 75/41 3,326,671 6/1967 Worner 75/40 3,632,335 l/l972 Worner 75/63 Primary ExaminerL. Dewayne Rutledge Assistant Examiner-Peter D. Rosenberg Attorney, Agent, or Firm-Burgess. Dinklage 8: Sprung [57] ABSTRACT 17 Claims, 2 Drawing Figures PROCESS FOR ACCELERATING METALLURGICAL REACTIONS The invention relates to a process for accelerating metallurgical reactions in a counter-current channel, with a stream of metal moved continuously in countercurrent to the slag, and to an apparatus for carrying out the process.

The desired object of continuous processing procedures in metallurgy is a counter-current process, in which the exchange of substance between the phases proceeds in a particularly favourable manner. Since the introduction of the electromagnetic counter-current channel has proved to be particularly advantageous in connection with production processes in the steel industry (Stahl und Eisen, 89, 1969, pages 1185/90), the further improvement in reactions in counter-current channels in accordance with the invention is hereinafter to be explained by reference to the particular example of an electromagnetic counter-current channel.

The counter-current process leads to a better utilisation of the slag and to lower final contents of the undesired impurities in the steel. When using an electromagnetic counter-current channel (German Offenlegungsschrift No. 1,433,631) with an inductor arranged beneath the channel, a layer or bed of thinly liquid metal with a thickness from below 1 cm to about 5 cm is provided in a channel-shaped reaction chamber. The travelling field generated by means of the inductor positively conveys the metal upwardly, while the slag flows downwardly under the action of gravity. It still has to be considered that, in the marginal region of the channel, the electric currents in the liquid metal flow parallel to the longitudinal axis of the channel and thus are unable to produce any forces on the metal in the longitudinal direction. For this reason, under the influence of gravity, there is obtained stoppage or reflux of the metal in this region, depending on the slope of the channel.

The earlier results when using a counter-current channel permitted it to be expected that not all metallurgical reactions proceed as satisfactorily as possible, and that possibly channels with very large dimensions have to be used. This requires a corresponding increase in expenditure and space requirements.

The invention has for its object to contribute to an acceleration, of the metallurgical reactions in countercurrent channels as hereinbefore defined. It more especially makes possible a shortening of the length of the necessary large installation for a counter-current channel which might otherwise have to be used. It also makes possible a reduction of the proportion of metal which generally flows back when using an electromagnetic counter-current channel.

According to this invention we provide a process for accelerating a metallurgical reaction in which metal and slag are produced, comprising moving a stream of the metal continuously in counter-current to the slag in a counter-current channel as hereinbefore defined, and for the purpose of forming a metal-slag emulsion injecting at least one jet of a gas having an inert, reducing or oxidising action on the melt depending on the nature of the reaction required into a marginal region of the channel, the said gas being injected parallel to and/or at an inclination to the predetermined boundary surface of the metal and slag or just above and/or just below the said boundary surface.

It is advantageous to inject a gas with an inert action on the melt together with a gas having a reducing or oxidising action on the melt.

It is advantageous to inject the or each gas jet in a pulsating manner and so to control the impulses of the injected gas stream that, on average, a substantially optimum metal droplet size for the reaction is produced. With steel/slag reactions, a mean value of the liquid steel droplets of about 1 to 2 mm is considered as optimal, taking into account the known deviations. The impulse of the gas jet or stream which causes the size of the metal droplets is determined through the pressure advantageously up to 20 atm and the crosssection of the gas jet issuing from a supply pipe.

It is to be preferred that, controlled through the amount of the metal-slag emulsion formed, the discharging slag is substantially free from metal droplets, while, following the path of the upwardly flowing metal, the emulsion formation is intensified. It may be appropriate to give the discharging slag, following the counter-current channel, an additional possibility of separation for the metal droplets which are still in the slag.

In another preferred form of the process, two gas jets are so arranged relatively to one another that essentially one gas jet causes a lifting of the slag and the other gas jet causes the droplet formation of the metal flowing therebeneath.

An additional acceleration of the metallurgical reaction can be produced by injecting a gas-forming substance and/or gas-yielding substance, with the gas jet or at least one of the gas jets. These substances can for example vaporise by contact with the metal or the slag or produce gas by reaction therewith. Such a substance injected with the or a gas jet can for example be limestone or a liquid hydrocarbon.

The process according to the invention is advantageously applied to the pre-refining or final refining of melts consisting of pig iron, scrap or similar initial material to form steel.

The use of an electromagnetic countercurrent channel is particularly preferred. With this use, it is advantageous if especially in a return flow region of the metal at least a part component of the impulse of the introduced total gas jet quantity acts in a conveying direction of the metal.

An apparatus for carrying out the process according to the invention comprises a counter-current channel as hereinbefore defined in which nozzles are passed through longitudinal side walls of the channel in the region of the predetermined boundary surface between metal and slag, the discharge directions of the nozzles being disposed parallel to or at an inclination to the predetermined boundary surface. In principle, it is preferred for the number of the nozzles to be increased in the direction of the slag supply with the object of an intensified metal/emulsion formation.

With nozzles arranged at an inclination, the angle of inclination towards the predetermined boundary surface is advantageously 30 to to the said boundary surface, especially approximately 45 to the said surface.

Nozzles having an inner diameter from 0.1 to 10 mm are advantageous.

The manner in which the process according to the invention operates may be understood from the following illustrative procedure.

If a section is taken of a counter-current channel perpendicular to a flowing slag and to a flowing metal, there is obtained here, with for instance pig iron or steel, a layer or bed height of approximately 1 to 3 cm with a slag height of to 50 cm. With the known counter-current process, the material transfer can only take place at the phase boundary surface of metal and slag over the width and total length of the channel. According to the invention, for the purpose of forming a metal-slag emulsion, a gas stream is injected into the phase boundary layer. By this means, the specific surface, which is produced from the ratio of metal/slag boundary surface to metal quantity, is raised considerably. By the raising of the specific surface, it is possible for the required metallurgical reaction on the countercurrent channel to be produced with considerably smaller geometrical dimensions than with the known processes.

As initially stated, a return flow of metal at the margin of the channel occurs for electrical reasons, whereby a complete change of substance in countercurrent is restricted. The gas stream or jet is preferably directed towards a return flow proportion of the metal at a margin of the channel. The impulse of the gas jet may be so chosen that there is formed a size of metal droplet which is the best possible for the reaction on the counter-current channel. A requirement for this purpose is that the droplets are not too small, so that they do not remain an excessively long time in the slag and are not carried downwards by the slag. On the other hand, the drops are not to be too large, so that firstly a sufficiently large specific surface is guaranteed and secondly the drops do not already drop back again into the metal after insufficient reaction with the slag. For steel-slag reactions, a steel droplet diameter of approximately 1 mm is aimed at. The size of droplets can be controlled by means of the impulse of the gas jet, it being known that the droplet size decreases with increasing energy.

From what has been described, it can be inferred that the metal, according to the process of the invention, is conveyed in drop form from the metal stream into the slag stream, where it reacts with the slag and then falls back again into the metal stream. It is to be taken into account here that the metal is conveyed about twenty times as quickly as the downwardly flowing slag, i.e., that with a sufficient residence time of the metal droplet in the downwardly flowing slag stream, the said droplet is only transported downwardly over an insignificant distance. The described cycle of the jumping metal droplet is repeated many times along the complete reaction path.

The advantages of the process according to the invention are more particularly shown in the following points:

With a continuous processing procedure on the counter-current channel, the same result can be produced with considerably smaller channel dimensions;

The heat balance of the procedure as described leads to a more favourable result;

The proportion of metal flowing back at a margin of the channel is reduced.

It is to be pointed out that limits are set for the described emulsification by the service life of the refractory material of the counter-current channel, more especially with a gas jet consisting of substantially pure oxygen. These disadvantages can be avoided or minimised by mixing with a gas inert to the said refractory material.

The invention is hereinafter described by reference to one constructional example. In the accompanying diagrammatic drawings:

FIG. 1 is a cross section through an electromagnetic counter-current channel.

FIG. 2 is a plan view of a part of the counter-current channel An inductor of a travelling field pump is indicated at I, the refractory base of a reaction chamber of the counter-current channel is indicated at 2 and the refractory side walls are shown at 3. The specifically heavier metal 4 flows lowermost in the channel and above this is the lighter slag 5. The boundary layer of slag and metal is indicated at 6. By means of nozzles 7, 8, 11 arranged in the side walls 3, the injection is into the boundary layer 6, or beneath the boundary layer 6, or above the boundary layer 6.

FIG. 2 shows a nozzle arrangement which additionally prevents the return flow of the metal at the margin of the counter-current channel. As shown by the indicated speed profile of the metal stream, the speed vector in the middle region is positively uphill at 10, while the speed is directed downwardly at 12 in the marginal region. With the provision of nozzles 8, which blow substantially into the slag, it is equally well possible to support the downwardly directed slag flow by an opposite inclined position.

Since the slag should discharge as far as possible free from metal droplets from the channel, an intensified emulsion formation occurs only in the direction towards the metal discharge. This intensified emulsion formation can be regulated by the number of the nozzles.

In one example of use, pig iron drops between 0.] and 2 mm, advantageously 0.5 to 1.5 mm, were produced with a nozzle of 1 mm inner diameter with a slope of 45 with respect to the stationary metal boundary surface with a pressure of 1 atm, the nozzle being situated about 5 mm below the metal boundary surface.

What we claim is:

l. A continuous metallurgical refining process in which metal and slag contact one another, comprising continuously moving a stream of the metal in countercurrent flow to continuously flowing slag in a countercurrent channel, injecting at least one jet of a gas into a marginal region of the channel, the said gas being injected parallel to and at an inclination to the region of the interface formed by the metal and the slag so as to form an emulsion of metal drops which are drawn into said slag whereby to accelerate the metal to slag interaction and reduce the length of the channel required for such interaction.

2. A process according to claim 1, wherein a gas having an inert action on the melt is injected together with a gas having a reducing action on the melt.

3. A process according to claim 1, wherein, controlled by the amount of the metal-slag emulsion formed, the discharging slag is substantially free from metal droplets, while the formation of emulsion is intensified, following the travel of the upwardly flowing metal.

4. A process according to claim 3, wherein two gas jets are so arranged relatively to one another that substantially one gas jet causes a lifting of the slag and the other gas jet causes droplet formation of the metal flowing therebeneath.

5. Process according to claim 4, wherein a gasforming substance is injected with the gas jet or at least one of the gas jets.

6. A process according to claim 5, which is applied to the pre-refining or final refining of a melt of pig iron, scrap or similar initial material for steel.

7. A process according to claim 6, wherein the counter-current channel is an electromagnetic countercurrent channel.

8. A process according to claim 7, wherein in a return flow region of the metal, at least a part component of the impulse of the total gas jet quantity acts in a metalconveying direction.

9. A metal treated by the process according to claim 1.

10. A process according to claim 1 wherein the gas is injected into the region of the interface formed by the metal and the slag at an angle of between 30 and 90 to said interface.

11. A process according to claim 1 wherein said slag is disposed over said metal, said slag moves in a generally downward direction and said metal moves in a generally upward direction.

12. A process according to claim 11 wherein the generally upward moving metal is in the form of a layer having a depth of between 1 and 5 centimeters and the slag has a depth of between 10 and 50 centimeters.

13. A process according to claim 12 wherein the slag and metal are disposed in an electromagnetic countercurrent channel.

14. A process according to claim 12 wherein the depth of the liquid metal is between 1 and 3 centimeters.

15. A continuous metallurgical refining process in which metal and slag contact one another comprising continuously moving a stream of the metal in countercurrent flow to continuously flowing slag in a countcrcurrent channel, injecting at least one jet of a gas into a marginal region of the channel, the gas being injected at an inclination to the region of the interface formed by the metal and the slag so as to form an emulsion in the direction of metal discharge of metal droplets drawn into said slag whereby to accelerate the metal to slag interreaction and reduce the length of the channel required for such interreaction.

16. A process according to claim 1 wherein a gas having an inert action on the melt is injected together with a gas having an oxidizing action on the melt.

17. A process according to claim 4 wherein a gasyielding substance is injected with the gas jet or at least one of the gas jets.

2 3" um'nan HATES m'x'm'r 0mm;

CERTIFICATE OF CORRECHQN Patent N0; 3,861,905 Dated Janu 21, 1975 gnventorgs) Eberhard Ste nmetz and Jurgen Kuhn It is certified that: error appearsim the aboye-identified patent and that said Letters Patent are hereby corrected as shown below:

Under Foreign Application Priority Data "2107263" should read "P 21 07 253.9

Under Assignee Sigried and sealed this 20th day of May 1975.,

(SEAL) Att st:

6 1 C, MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. A CONTINUOUS METALLURGICAL REFINING PROCESS IN WHICH METAL AND SLAG CONTACT ONE ANOTHER, COMPRISING CONTINUOUSLY MOVING A STREAM OF THE METAL IN COUNTER-CURRENT FLOW TO CONTINUOUSLY FLOWING SLAG IN A COUNTER-CURRENT CHANNEL, INJECTING AT LEAST ONE JET OF A GAS INTO A MARGINAL REGION OF THE CHANNEL, THE SAID GAS BEING INJECTED PARALLEL TO AND AT AN INCLINATION TO THE REGION OF THE INTERFACE FORMED BY THE METAL AND THE SLAG SO AS TO FORM AN AMULSION OF METAL DROPS WHICH ARE DRAWN INTO SAID SLAG WHEREBY TO ACCELERATE THE METAL TO SLAG INTERACTION AND REDUCE THE LENGTH OF THE CHANNEL REQUIRED FOR SUCH INTERACTION.
 2. A process according to claim 1, wherein a gas having an inert action on the melt is injected together with a gas having a reducing action on the melt.
 3. A process according to claim 1, wherein, controlled by the amount of the metal-slag emulsion formed, the discharging slag is substantially free from metal droplets, while the formation of emulsion is intensified, following the travel of the upwardly flowing metal.
 4. A process according to claim 3, wherein two gas jets are so arranged relatively to one another that substantially one gas jet causes a lifting of the slag and the other gas jet causes droplet formation of the metal flowing therebeneath.
 5. Process according to claim 4, wherein a gas-forming substance is injected with the gas jet or at least one of the gas jets.
 6. A process according to claim 5, which is applied to the pre-refining or final refining of a melt of pig iron, scrap or similar initial material for steel.
 7. A process according to claim 6, wherein the counter-current channel is an electromagnetic counter-current channel.
 8. A process according to claim 7, wherein in a return flow region of the metal, at least a part component of the impulse of the total gas jet quantity acts in a metalconveying direction.
 9. A metal treated by the process according to claim
 1. 10. A process according to claim 1 wherein the gas is injected into the region of the interface formed by the metal and the slag at an angle of between 30* and 90* to said interface.
 11. A process according to claim 1 wherein said slag is disposed over said metal, said slag moves in a generally downward direction and said metal moves in a generally upward direction.
 12. A process according to claim 11 wherein the generally upward moving metal is in the form of a layer having a depth of between 1 and 5 centimeters and the slag has a depth of between 10 and 50 centimeters.
 13. A process according to claim 12 wherein the slag and metal arE disposed in an electromagnetic counter-current channel.
 14. A process according to claim 12 wherein the depth of the liquid metal is between 1 and 3 centimeters.
 15. A continuous metallurgical refining process in which metal and slag contact one another comprising continuously moving a stream of the metal in counter-current flow to continuously flowing slag in a counter-current channel, injecting at least one jet of a gas into a marginal region of the channel, the gas being injected at an inclination to the region of the interface formed by the metal and the slag so as to form an emulsion in the direction of metal discharge of metal droplets drawn into said slag whereby to accelerate the metal to slag interreaction and reduce the length of the channel required for such interreaction.
 16. A process according to claim 1 wherein a gas having an inert action on the melt is injected together with a gas having an oxidizing action on the melt.
 17. A process according to claim 4 wherein a gas-yielding substance is injected with the gas jet or at least one of the gas jets. 